1. Field of the Invention
The present invention relates to a production method of a disk drive device provided with a bearing unit and to a disk drive device produced by the production method.
2. Description of the Related Art
In recent years, there has been demand for disk drive devices, such as an HDD (Hard Disk Drive), of a smaller size and larger capacity. For example, in a disk drive device that magnetically records data, a recording disk having a recoding track is rotated at high speed, and a magnetic head reads or writes the data while floating over the recoding track, keeping a slight space above the recoding track. In order to provide a disk drive device of a small size and large capacity, the width of the recording track needs to be smaller. In order to realize the miniaturization of the width of the recording track, it is necessary to have an even smaller space between the magnetic head and the recording disk. The size of the space between the magnetic head and the recording disk needs to be extremely small, for example, 10 nm at most.
For the miniaturization of the disk drive devices, magneto-resistance devices (hereinafter, referred to as “MR devices”) are used for magnetic heads. Meanwhile, the use of an MR device in an extremely small space may cause thermal asperity failure (hereinafter, referred to as “TA failure”) and head crash failure in the magnetic head. More specifically, TA failure is a failure where fine foreign particles on the surface of a recording disk come into contact with an MR device when the magnetic head floats and traces, instantaneously producing heat in the MR device by the kinetic energy of the particles while instantaneously heating or cooling the MR device, such that the resistance value of the MR device changes instantaneously and that the changed resistance value is included in a reproduced signal as noise, which prevents the reproduced signal from being correctly read out.
According to the research conducted by the inventors of the present invention, it is found that TA failure is caused by the attachment of foreign particles (hereinafter, referred to as “particles”) of 0.1 μm to several μm, which were attached to the inside of a disk drive device, to the surface of a recording disk by vibration or air flow. Patent document 1 describes a cleaning device that cleans various parts including a base member.
[Patent document 1] Japanese Patent Application Laid-open 7-124529
Even if members such as, for example, a hub or a bearing unit, which constitute a disk drive device are cleaned, a lubricant can stick to the hub when the lubricant is put in the bearing unit after the bearing unit is combined to the hub. For example, a lubricant that is attached to assembly equipment or tools, or to a worker's hands can stick to the hub. The lubricant attached to the hub can be in the form of particles.
The particles that are attached during the assembly as described above cannot be removed by a conventional production method of the disk drive device, and the general standard of the cleanliness inside of a disk drive device is very low. When a lot of particles stay, the possibility that TA failure may occur increases in the case where the gap for a magnetic head to float is made small, hindering a disk drive device from having small size and large capacity.